Interaction of Permanent Cylindrical Magnets with Axial Magnetization

Known equivalence of the field of a permanent magnet having the fonn of a circular cylinder and axial magnetization and that of the field of a circular tape with constant surface current is used. Exact calculation of potential energy of interaction between two circular currents makes it possible: 1) to express in accurate formulae force and moment characteristics of interaction between magnets; 2) retaining the second-order memebers with respect to small displacements of two initially coaxial rings to build "the stiffness matrix" and analyse quantitatively the known static unstabiIity of the system. One of the possible rotor suspension configurations with permanent magnets is given to illustrate why the main quantitative characteristic of unstability - negative relationship of eigenvalues of the stiffness matrix - remains valid for all axially symmetric systems.